Washing machine

ABSTRACT

The field weakening of the magnetic flux of a permanent magnet is enabled. The rotor of the permanent magnet dynamo-electric machine is divided to move relatively.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an electric motor which uses apermanent magnet as a field magnet, particularly to an electric motorfor driving a washing machine and a control method thereof, and relatesto an electric motor and a control method thereof in which positions ofthe magnetic pole centers of said first field magnet and said secondfield magnet can be changed, and the amount of the effective magneticflux can be changed according to the number of revolution.

[0002] In a permanent magnet field type electric motor of the prior art,an induced electromotive force E is determined by a constant magneticflux Φ generated by a permanent magnet arranged in a rotor and arotating angular speed ω of the motor. That is, when the rotatingangular speed ω (rotating speed) of the motor is increased, the inducedelectromotive force is proportionally increased.

[0003] Accordingly, high torque can be obtained in a low speed range,but operation in a high-speed range is difficult because the variablerange of rotating speed is narrow. Therefore, it may be considered thatthe high-speed operation range is widened using a field weakeningcontrol technology.

[0004] Moreover, the torque of the electric motor is transmitted by thebelt and the gear through pulley so that the electric motor of thewashing machine may secure a fixed power output in a wide speed range.However, there is a direct drive method of transmitting the torque ofthe electric motor directly to the body of revolution and thespin-drying drum such as pulsators recently.

[0005] There is a big problem with large noises of the sliding and theshock sound etc. of the belt and the gear when the torque of an electricmotor is transmitted by the belt and the gear through pulley in theconventional washing machine.

[0006] Moreover, expanding a high-speed operating range by using saidfield-weaking control technology has the limit in the direct drivemethod of transmitting the torque of the electric motor directly to thebody of revolution (for instance, pulsator etc.) and spin-drying drumsdue to the heat generation by the field weakening electric current andthe decrease in efficiency, etc. Because said direct drive method doesnot have the speed reducer, the electric motor which can cover awide-ranging speed region of the washing and the rinsing operation bylow-speed high torque and the spin-drying operation by high-speed largepower becomes large-scale.

SUMMARY OF THE INVENTION

[0007] In the present invention, the following washing machine is used.The washing machine comprises a washing spin-drying drum pivotted freelyaround a rotation axis in the outside tank, a body of revolutionpivotted freely around a rotation axis whose center is the same as oneof said rotation axis at the bottom of said washing spin-drying drum, achange-over mechanism for connecting or releasing the rotation axis ofsaid washing spin-drying drum to the rotation axis of the body ofrevolution, and an electric motor, whereby washing or rinsing operationis carried out by rotating forward or reversely the body of revolutionto stir the inside of said washing spin-drying drum, and thenspin-drying operation is performed.

[0008] Said electric motor comprises a stator having a primary windingand a rotor having a field magnet, said field magnet comprising a firstfield magnet having different polarity magnetic poles sequentiallyarranged in a rotating direction and a second field magnet havingdifferent polarity magnetic poles sequentially arranged in a rotatingdirection, said first and said second field magnets being opposite tomagnetic poles of said stator; and a mechanism for changing a phase of acomposite magnetic pole of said first and said second field magnets withrespect to the magnetic pole of said first field magnet depending on adirection of torque, said mechanism for changing depending on adirection of torque comprising means for making magnetic pole centers ofequal-polarity of said first and said second field magnets in phase by adirection of torque generated in said rotor and by balance of magneticaction forces between said first and said second field magnets; andmeans for making the magnetic pole centers of said first and said secondfield magnets out of phase when the direction of torque generated in therotor is reversed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic diagram showing a washing machine having anembodiment of a permanent magnet type synchronous motor.

[0010]FIG. 2 is a schematic view showing a case (a first case) wheremagnetic pole centers of equal-polarity of the rotor of the motor inFIG. 1 are out of phase.

[0011]FIG. 3 is a schematic view showing a case where magnetic polecenters of equal-polarity of the rotor of the motor in FIG. 1 are inphase.

[0012]FIG. 4 is a schematic view showing a case (a second case) wheremagnetic pole centers of equal-polarity of the rotor of the motor inFIG. 1 are out of phase.

[0013]FIG. 5 is graphs showing various kinds of characteristics versusrotating speed of the motor in FIG. 1.

[0014]FIG. 6 is a control block diagram of the motor in FIG. 1.

[0015]FIG. 7 is a view showing another embodiment of a motor inaccordance with the present invention (an actuator in OFF state).

[0016]FIG. 8 is a view showing another embodiment of a motor inaccordance with the present invention (an actuator in ON state).

[0017]FIG. 9 is a view showing the inside of the rotor of anotherembodiment of a motor in accordance with the present invention.

[0018]FIG. 10 is a view showing the inside of a rotor of anotherembodiment of a motor in accordance with the present invention.

[0019]FIG. 11 is a view showing another embodiment of a motor inaccordance with the present invention (an actuator in ON state).

[0020]FIG. 12 is a schematic view showing measurement of axial directiondisplacement in another embodiment of a motor in accordance with thepresent invention.

[0021]FIG. 13 is a schematic view showing a rotor of another embodimentof a motor in accordance with the present invention (adding gapdifference).

[0022]FIG. 14 is a view showing another embodiment of a motor inaccordance with the present invention

[0023]FIG. 15 is a schematic view showing a rotor of another embodimentof a motor in accordance with the present invention (a case where thepresent invention is applied to a 8-pole motor).

[0024]FIG. 16 is a schematic view showing the arragement of anotherembodiment of a motor in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Embodiments of the present invention are explained hereinafter.

[0026]FIG. 1 shows the outline of the washing machine in which thepermanent magnet type synchronous motor according to this embodiment isprovided.

[0027] The permanent magnet field type synchronous motor which drivesdirectly pulsator 73 is used as electric motor 2. Electric motor 2rotates pulsator 73 and spin-drying drum 72 through the clutch.

[0028] In washing machine case 70 shown in FIG. 1, there are outsidetank 71 and washing spin-drying drum 72. This is a washing machine whichcomprises a washing spin-drying drum pivotted freely around rotationaxis 22 in outside tank 71, pulsator 73 pivotted freely around arotation axis whose center is the same as one of said rotation axis atthe bottom of said washing spin-drying drum, change-over mechanism 77for connecting or releasing the rotation axis of said washingspin-drying drum to the rotation axis of said pulsator, and electricmotor 2, whereby washing or rinsing operation is carried out by rotatingforward or reversely the body of revolution to stir the inside of saidwashing spin-drying drum, and then spin-drying operation is performed.There are two type washing machines. In one type, the water is collectedonly in the spin-drying drum, and in the other type, the water isaccumulated in the whole water tank 71 including the spin-drying drum,when the rinsing is carried out. The present invention can be applied tothe washing machine of which type.

[0029] The washing machine of such configuration is driven by inverter78. This inverter requires the control by a microcomputer, and is anelectric motor control circuit with the function as the rotation controlmeans for changing the number of revolution by receiving an instructionfrom the microcomputer. The microcomputer control circuit is built intothe inverter. Inverter 78 has the function as a motor electric currentdetection means by which the current value which flows to electric motor2 is detected. Moreover, drain valve 74, system control panel 75, andwater level sensor 76, etc. are further provided as the basic componentelement of the washing machine.

[0030]FIG. 2 is a schematic view showing a case where the centers ofequal-polarity of the rotor of the motor shown in FIG. 1 are out ofphase.

[0031] In FIG. 3, armature windings 11 are wound and set inside slots ofa stator core 10, and bonded to a housing 13 having cooling paths 12inside of which coolant flows.

[0032] The rotor of a permanent magnet embedded type 20 is composed of afirst rotor 20A fixed to a shaft 22 and a second rotor 20B separatedfrom the shaft 22. of course, the rotor may be a rotor of a surfacemagnet type instead of the rotor of a permanent magnet embedded type.

[0033] In the first rotor 20A, permanent magnets 21A are arranged so asto be alternatively aligned magnetic poles of different polarity in therotating direction. Similarly, in the first rotor 20B, permanent magnets21B are arranged so as to be alternatively aligned magnetic poles ofdifferent polarity in the rotating direction. The field magnetscoaxially arranged in the two rotors of the first and the second rotorsare opposite to magnetic poles of the stator.

[0034] A nut portion 23B is formed in the inner side of the second rotor20B, and a bolt screw portion 20A to be in contact with the nut portion23B is formed in the shaft. By connecting the second rotor 20B with theshaft with the screw function, the second rotor 20B is movable in theaxial direction while being rotated with respect to the shaft.

[0035] Further, a stopper 24 is arranged at a position apart from theside surface of the second rotor 20B so that the second rotor 20B maynot exceed a preset displacement from the center of the stator.Furthermore, by providing a servo mechanism of an actuator 25 fordriving the stopper to make the stopper movable in the direction ofshaft axis, the displacement between the magnetic pole centers of thefirst field magnet and the second field magnet can be varied. As theresult, it is possible to control the total effective magnetic fluxcomposed of the first field magnet and the second field magnet to thestator having the armature windings in the slits.

[0036] Description will be made below on that the effective magneticflux of the permanent magnets can be varied corresponding to thedirection of torque by doing as described above.

[0037] In an electric motor basically using armature windings in thestator and permanent magnets in the rotor, in the case that the rotatingdirection of the rotor is the same between when the motor is working asa motor and when working as a generator, the direction of the torqueacting on the rotor becomes opposite. between when the motor is workingas a motor and when working as a generator.

[0038] On the other hand, in the case that the motor is working as amotor, the direction of the torque is reversed when the rotatingdirection of the rotor is reversed. Similarly, in the case that themotor is working as a generator, the direction of the torque is reversedwhen the rotating direction of the rotor is reversed.

[0039] When the basic theory in regard to the rotating direction and thetorque direction described above is applied to the embodiment of themotor in accordance with the present invention, the following can besaid.

[0040] When the washing machine is driven in the low rotating speedregion, for example, the washing or rinsing operation in which a bigtorque is needed, the high torque characteristic is obtained bycompulsorily making the centers of equal-polarity of first rotor 20A andsecond rotor 20B arranged, and increasing the amount of the effectivemagnetic flux by the stator magnetic pole and the opposed permanentmagnet as shown in FIG. 3.

[0041] Next, when the electric motor is operated in a high rotatingspeed range, for example, spin-drying operation, the centers ofequal-polarity of the first rotor 20A and the second rotor 20A arebrought out of phase while the second rotor 20B is being moved withrespect to the shaft 22 to widen the gap between the first rotor 20A andthe second rotor 20A as if the nut portion were screwed off from thebolt screw portion, as shown in FIG. 4. Therefore, the effectivemagnetic flux by the stator magnetic poles and the opposite permanentmagnets is decreased. In other words, there is the weakening magneticfield effect, and a high output power characteristic can be obtained inthe high rotating range.

[0042]FIG. 4 schematically shows the state that the effective magneticflux by the stator magnetic poles and the opposite permanent magnets isdecreased by making the centers of equal-polarity of the first rotor 20Aand the second rotor 20A out of phase while the gap between the firstrotor 20A and the second rotor 20B is being widened.

[0043] In FIGS. 3 and 4, there are associative illustrations of a headportion 61 of a bolt, a bolt screw portion 60 and a nut portion 62. Thehead portion 61 of the bolt corresponds to the first rotor 20A, the nutportion 62 corresponds to the second rotor 20B. When the bolt screwportion 60 (corresponding to the part 23A in FIG. 2) is rotating adirection, the nut portion 62 is fastened or unfastened depending on thedirection of torque acting on the nut portion 62. The similar phenomenonoccurs in the second rotor 20B depending on the direction of torqueacting on the rotor.

[0044] On the other hand, in the case that the motor is working as anelectric motor, the directions of the torque in the forward rotation andthe backward rotation are opposite each other. Therefore, if FIG. 3shows the state of the forward rotation, FIG. 4 shows the state of thebackward rotation.

[0045] A nut portion 23B is formed in the inner side of the second rotor20B, and a bolt screw portion 20A to be in contact with the nut portion23B is formed in the shaft. Both of them are connected by using thescrew function. Although the states shown in FIGS. 3 and 4 are oppositeeach other if the direction of the screw is reversed (for instance, froma left screw to a right screw), the same effect is obtained. Secondrotor 20B is movable in the axial direction while being rotated withrespect to the shaft.

[0046] When the electric motor is operated in the washing or rinsingoperation, high torque characteristic can be obtained by making thecenters of equal-polarity magnetic poles of the first rotor 20A and thesecond rotor 20B are made in phase to increase the effective magneticflux by the stator magnetic poles and the opposite permanent magnets, asshown in FIG. 3, even if it is in the forward rotation operation or thebackward rotation operation.

[0047] Next, when the electric motor is operated in a high rotatingspeed range, for example, spin-drying operation, the centers ofequal-polarity of the first rotor 20A and the second rotor 20B arebrought out of phase while the second rotor 20B is being moved withrespect to the shaft 22 to widen the gap between the first rotor 20A andthe second rotor 20B as if the nut portion were screwed off from thebolt screw portion, as shown in FIG. 4. Therefore, the effectivemagnetic flux by the stator magnetic poles and the opposite permanentmagnets is decreased. In other words, there is the weakening magneticfield effect, and a constant output power characteristic can be obtainedin the high rotating range.

[0048] Description will be made below on operation of the inducedelectromotive force by the electric motor in accordance with the presentinvention.

[0049]FIG. 5 shows the characteristics of the effective flux, theinduced electromotive force and the terminal voltage versus the angularrotating speed of the permanent magnet synchronous motor.

[0050] The induced electromotive force E is determined by a constantmagnetic flux Φ generated by the permanent magnets arranged in the rotorand an angular rotating speed ω of the electric motor. That is, as shownin FIG. 6(a), if the constant magnetic flux Φ1 is constant, the inducedelectromotive force E1 is proportionally increased as the angularrotating speed ω (rotating speed) is increased. However, since there isa limitation in the output voltage of the inverter due to the terminalvoltage of the power supply and the capacity of the inverter, there isalso a limitation in the induced electromotive force generated by theelectric motor under a normal operating condition. Therefore, in thepermanent magnet synchronous motor, it is necessary in a range above arotating speed to perform what is called the field weakening control inorder to reduce the magnetic flux generated by the permanent magnets.

[0051] Since the induced electromotive force-is increased in proportionto the angular rotating speed, the current of the field weakeningcontrol must be increased. Therefore, a large current needs to beconducted to the coil of primary conductor, and consequently the heatgenerated in the coil is increased, which may result reducing of theefficiency as a motor in a high rotating speed range and demagnetizationof the permanent magnets due to heat generation exceeding the coolingcapacity.

[0052] For example, as shown in FIG. 5(a), when the magnetic flux Φ1generated by the permanent magnets arranged in the rotor is changed tothe magnetic flux Φ2 at a point of the angular rotating speed ωl(rotating speed), the induced electromotive force E1 of the motor ischanged to the induced electromotive force E2. By this characteristic,the maximum value of the induced electromotive force can be limited.

[0053] Similarly, FIG. 5(b) is a schematic graph showing that when themagnetic flux Φ is changed little by little corresponding to the angularrotating speed ω (rotating speed), the induced electromotive force E canbe maintained constant.

[0054] In an embodiment of a means for obtaining the characteristicsshown in FIG. 6, the first field magnet of a motor is fixed to a shaft,and the second field magnet is separated from the shaft. The shaft andthe second field magnet have screw functions to be connected to eachother by forming a bolt screw portion in the shaft and a nut portioninside the second field magnet. Further, a stopper is provided at aposition apart from a side surface of the second field magnet, and aservo mechanism capable of moving the stopper in parallel to the shaftaccording to a rotating speed is provided.

[0055]FIG. 6 shows the control block of electric motor 2 of FIG. 1.

[0056] First of all, drive judgment part 101 judges the drive operationof permanent magnet type synchronous motor 2 based on the setinformation from system control panel (75 in FIG. 1), the informationfrom water level sensor 76 and the number of revolution of permanentmagnet type synchronous motor 2, and outputs the electric currentinstruction value.

[0057] The output from current control block 102 is converted into athree-phase alternating current in rotational coordinate transformationpart 103, and controls permanent magnet type synchronous motor 2. Eachphase current of permanent magnet type synchronous motor 2 is convertedinto the biaxial current by detecting each phase current (at least twophase currents) and the number of revolution, and fed back to thecurrent instruction value. Further, the number of revolution, themagnetic pole position, etc. are detected by detector 106, and fed backto each control block through magnetic pole position transformation part107 and speed transformation part 108.

[0058] Although the embodiment of FIG. 7 comprises a position-and-speedsensor of the motor 2 and a current sensor of the motor, a controlcircuit of a sensor-less structure for driving the motor 2 without partof these sensors may be applicable.

[0059] Further, since in the permanent magnet synchronous motor of thepresent invention, the pole centers of equal-polarity of the first andthe second rotors are brought in phase or out of phase corresponding tothe operating condition, the permanent magnet synchronous motor of thepresent invention has a function of correcting a lead angle of currentsupply by a controller for controlling the inverter corresponding to apositional shift angle of the composite magnetic pole of the first fieldmagnet and the second field magnet.

[0060] An embodiment for correcting the lead angle of current supplywill be described below.

[0061] When the motor is operated by fixing the first field magnet to ashaft, by separating the second field magnet from the shaft, and byforming a bolt screw portion in the shaft and a nut portion inside thesecond field magnet to add screw functions to be connected to each otherto the shaft and the second field magnet, the second filed magnet ismoved in the axial direction while being rotated.

[0062]FIG. 12 shows the relationship between rotation angle anddisplacement in the axial direction when the pole centers ofequal-polarity of the first rotor and the second rotor are in phase orout of phase corresponding to the operating condition.

[0063] Referring to FIG. 12, since there is a proportional relationshipbetween the rotation angle θ and the axial displacement ΔL of the secondrotor, the axial displacement ΔL is measured using a displacement meter64, and fed back to the position detecting circuit (the referencenumeral 106 in FIG. 6) of the control circuit to be used for optimumcontrol to correct the lead angle of current supply as a converted valueof the shift angle of the composite magnetic pole position of the firstfield magnet and the second field magnet.

[0064]FIG. 7 is a view showing another embodiment of a motor inaccordance with the present invention.

[0065] The first rotor 20A is fixed to the shaft 22, the second rotor20B being separated from the shaft 22, the bolt screw portion 23A beingformed in part of the shaft, a sleeve 41 being fixed to the inside ofthe second field magnet, the nut portion 23B being fixed to the insideof the sleeve 41. Thus, the second rotor 20B is rotated with respect tothe first rotor 20A while the gap between the first rotor 20A and thesecond rotor 20B is being widened as if a nut portion were screwed offfrom a bolt screw portion.

[0066] When change in flux linkage occurs between the inside of thesecond field magnet and the shaft 22 as the second rotor is rotatedbecause there is a small play between the second field magnet and theshaft 22, a trouble such as electrolytic corrosion may occur. Therefore,the sleeve 41 is made of a non-magnetic material having an electricresistivity higher than that of iron. By doing so, the inside of thesecond field magnet and the shaft 22 are magnetically and electricallyinsulated by the sleeve 41.

[0067] Supporting mechanisms 40A, 40B are arranged inside the sleeve 41so as to guide rotating motion, reciprocal motion and the compositemotion between the second field magnet and the shaft.

[0068] The second rotor 20B is connected to the shaft by forming a screwfunction of the bolt screw portion 23A in part of the shaft, and amovable stopper 24 is arranged at a position apart from a side surfaceof the second field magnet, and supporting mechanisms 42, 47 arearranged between the stopper 24 and the shaft, and between the stopperand the side surface of the second rotor 20B so as to guide rotatingmotion, reciprocal motion and the composite motion between the secondrotor with respect to the shaft. The supporting mechanism 42 has afunction of a thrust bearing, and the supporting mechanism 47 has afunction of guiding the rotating motion, the reciprocal motion and thecomposite motion though it is a radial bearing.

[0069] Further, there is an effect that the function of the supportingmechanism 42 is improved as the thrust bearing by arranging a spring 48.

[0070] Description will be made below on a magnetic clutch as an exampleof the servomechanism capable of moving the stopper 24 in parallel tothe shaft.

[0071] The structure of the magnetic clutch is that a coil 46 is woundaround a yoke 44, and a stopper 24 may also serve as a movable core. Theyoke 44 and the coil 46 are fixed to a frame 49 of the motor or to apart of the compressor, not shown, and a spring 45 is arranged betweenthe yoke 44 and the stopper 24 so as to have a function of a resetdevice at braking excitation. A bearing 50 is arranged between the frame49 and the shaft 22 to support the shaft 22.

[0072]FIG. 7 shows the coil 46 under a non-excited state, and FIG. 8shows the coil 46 under an excited state.

[0073] The yoke 44 becomes a strong magnet by exciting the coil 46 toattract the stopper 24 also having the function as the movable core.

[0074] Next, when stopper 24 is attracted by exciting coil 46, thetorque is applied while the second rotor 20B is being moved with respectto the shaft 22 to widen the gap between the first rotor 20A and thesecond rotor 20B as if the nut portion were screwed off from the boltscrew portion, as shown in FIG. 4. Therefore, the burden of the currentflown to coil 46 is decreased.

[0075] When the stopper 24 is attracted by exciting the coil 46, burdenof conducting current to the coil 46 can be reduced by adding torque tothe second rotor 20B so as to be rotated with respect to the first rotor20A while the gap between the first rotor 20A and the second rotor 29Bis being widened as if a nut portion were screwed off from a bolt screwportion.

[0076]FIG. 9 shows an example of the sleeve 41 to be fixed to the insideof the second rotor 20B.

[0077] As one of methods of fixing the second rotor and the shaft, thesecond rotor 20B and the sleeve 41 are fixed by forming projected anddepressed portions on the contact surfaces of the two parts. Differencein the structure of the inside portions between the first rotor 20Afixed to the shaft 22 and the second rotor 20B separated from the shaft22 is shown in FIG. 9.

[0078]FIG. 10 shows another embodiment of the present invention.

[0079] A depressed portion 53 is formed on a side surface of the firstfield magnet where the first field magnet and the second field magnetare in contact with each other, and a projected portion 54 also servingas the function of the sleeve is formed in the second field magnet. Theprojected portion 54 and the sleeve 41 may be formed in a unit. By doingso, a sufficient space for the sleeve 41 can be secured. Therefore, thisis one of methods of obtaining a motor having the second rotor of a thinaxial thickness by effectively arranging the spring 48, the supportingmechanisms 40A, 40B and the nut portion 23B.

[0080]FIG. 11 shows another embodiment of the present invention.

[0081] The basic components shown in FIG. 11 are the same as those ofFIG. 7, but a part corresponding to the magnetic clutch is changed. FIG.11 shows the coil 46 under the excited condition, and the yoke 44 isdetached from the stopper 24 by the spring 45 at cutting off theexcitation. Further, the embodiment has a characteristic that a thrustforce is applied to the second rotor 20B by the screw function due to aninteraction between the bolt screw portion 23A on which torque isapplied and the nut portion 23B. Therefore, when the excitation of thecoil 46 is cut off, the stopper 24 is detached from the yoke 44 byadding the thrust force to push out the stopper 24 due to theinteraction between the screw and the torque. The yoke 44 is fixed tothe frame 49 through an arm 52, or to a part of the compressor, notshown.

[0082] Similarly to FIGS. 7 and 8, the magnetic clutch shown in FIG. 11is an example of a servo mechanism capable of moving the stopper 24 inparallel to the shaft, positioning of the stopper can be more accuratelyperformed by employing a hydraulic actuator, a linear driving deviceusing a rotor and a ball screw, a linear motor or the like.

[0083]FIG. 13 shows other embodiments of the present invention.

[0084] The motor in accordance with the present invention ischaracterized by that the first rotor 20A is firmly fixed to the shaft22, but the second rotor 20B has freedom to the shaft. Therefore, thereis a small play in the mechanical dimension between the second rotor 20Band the shaft 22, and accordingly the second rotor 20B may becomeeccentric when large torque or a centrifugal force is applied to thesecond rotor 20B. The air gap Gap 2 between the second rotor 20B havingthe second field magnet and the stator is made larger than the air gapGap 1 between the first rotor 20A having the first field magnet and thestator. By doing so, the mechanical contact between the second rotor 20Band the stator caused by decentering can be prevented.

[0085] A plurality of springs 48 and 51 are arranged between the stopper24 and the second rotor 20B and between the first rotor 20A and thesecond rotor 20B, respectively. Thereby, there is an effect in thatrapid fluctuation in the second rotor 20B can be suppressed, and motionof the second rotor 20B by the torque direction can be assisted.

[0086] Of course, the component parts shown by the figures can becombined by various methods, or can be added or eliminated depending onthe purpose of use.

[0087]FIG. 14 shows the dynamo-electric machine according to anotherembodiment of the present invention.

[0088] This is a permanent magnet type synchronous dynamo-electricmachine in which screw 23 of the second rotor shown in FIG. 2 iseliminated, and the mechanism where the rotating angle θ can be moved isprovided.

[0089] The concavo-convex portion is provided to shaft 22 like thecogwheel instead of the screw part of the second rotor shown in FIG. 2,and the convexo-concave portion is provided to insert the shaft on theinner diameter side of the second rotor. However, only fixed rotatingangle θ can be moved by enlarging the width of the ditch more than thewidth of the engaging teeth when shaft 22 is inserted into the innerdiameter side of the second rotor. Further, a rapid collision can besoftened by providing spring 26 and dumper 27 between the engaging teethand ditches. Similarly, an actuator is provided. When the washingmachine is driven in the low rotating speed region, for example, thewashing or rinsing operation in which a big torque is needed, the hightorque characteristic is obtained by compulsorily making the centers ofequal-polarity of first rotor 20A and second rotor 20B arranged, andincreasing the amount of the effective magnetic flux by the statormagnetic pole and the opposed permanent magnet as shown in FIG. 3.

[0090] Next, when the electric motor is operated in a high rotatingspeed range, for example, spin-drying operation, the center ofequal-polarity of the second rotor 20B is brought out of phase withrespect to shaft 22, as shown in FIG. 14. Therefore, the effectivemagnetic flux by the stator magnetic poles and the opposite permanentmagnets is decreased. In other words, there is the weakening magneticfield effect, and a high output power characteristic can be obtained inthe high rotating range.

[0091] Although the above explanation of the present invention has beenmade on the four-pole motor, there is no need to say that the presentinvention can be applied to a two-pole motor or a six-pole motor. As anexample, FIG. 15 is a schematic view showing a rotor of a permanentmagnet synchronous motor in which the present invention is applied to aneight-pole motor. Further, the present invention can be applied to anytype of rotor, an embedded magnet type or a surface magnet type.

[0092]FIG. 16 is a schematic view showing washing machines of a directdrive method type and of a gear-combined method type.

[0093] In FIG. 16, the component parts except the gear are provided incommon. FIG. 16(a) shows the direct drive method, and FIG. 16(b) showsthe gear-combined method. In FIG. 16 (b), gear 79 is provided on theshaft of said washing spin-drying drum and between change-over mechanism(77 of FIG. 1) for connecting or releasing to the shaft of said pulsator(73 of FIG. 1) and electric motor 2. The gear can be installed inchange-over mechanism 77. Of course, it is needless to say that both areapplicable as an electric motor of the present invention.

[0094] Since the permanent magnet synchronous motor in accordance withthe present invention is constructed in that the rotors divided into thefirst field magnet and the second field magnet are arranged on thesingle shaft, and the pole centers of the first and the second fieldmagnets are varied depending on the direction of torque, there is theeffect that the effective magnetic flux by the permanent magnetsopposite to the stator magnetic poles can be varied.

[0095] Particularly, weakening magnetic filed control of the motor forthe compressor of the air conditioner can be easily performed, andaccordingly there is the effect of the wide range variable speedcontrol.

What is claimed is:
 1. A washing machine comprising a washingspin-drying drum pivotted freely around a rotation axis in the outsidetank, a body of revolution pivotted freely around a rotation axis whosecenter is the same as one of said rotation axis at the bottom of saidwashing spin-drying drum, a change-over mechanism for connecting orreleasing the rotation axis of said washing spin-drying drum to therotation axis of the body of revolution, and an electric motor, wherebywashing or rinsing operation is carried out by rotating forward orreversely the body of revolution to stir the inside of said washingspin-drying drum, and then spin-drying operation is performed, whereinsaid electric motor comprises; a stator having a primary winding and arotor having a field magnet, said field magnet comprising a first fieldmagnet having different polarity magnetic poles sequentially arranged ina rotating direction and a second field magnet having different polaritymagnetic poles sequentially arranged in a rotating direction, said firstand said second field magnets being opposite to magnetic poles of saidstator; and a mechanism for changing a phase of a composite magneticpole of said first and said second field magnets with respect to themagnetic pole of said first field magnet depending on a direction oftorque, said mechanism for changing depending on a direction of torquecomprising means for making magnetic pole centers of equal-polarity ofsaid first and said second field magnets in phase by a direction oftorque generated in said rotor and by balance of magnetic action forcesbetween said first and said second field magnets; and means for makingthe magnetic pole centers of said first and said second field magnetsout of phase when the direction of torque generated in the rotor isreversed.
 2. A washing machine according to claim 1, wherein saidelectric motor comprises a means for making said first and said secondfield magnets in phase at an initial position; and a means for makingthe magnetic pole centers of said first and said second field magnetsout of phase with each other, and said mechanism for changing themagnetic pole centers depending on change in the direction of torque isconstructed so that said first field magnet may be fixed to a shaft, andsaid second field magnet may be separated from said shaft, and themagnetic pole center of said first field magnet and the magnetic polecenter of said second field magnet may be made to be out of phase byforming said shaft and said second field magnet relatively movable fromeach other within an angle corresponding one pole of the magnetic pole.3. A washing machine according to claim 1 or 2, which uses an electricmotor comprising: said mechanism for changing the magnetic pole centersdepending on change in the direction of torque, said mechanism beingconstructed so that said first field magnet may be fixed to a shaft, andsaid second field magnet may be separated from said shaft, and saidshaft and said second field magnet have screw functions to be connectedto each other by forming a bolt screw portion in said shaft and a nutportion inside said second field magnet; a stopper at a position apartfrom a side surface of said second field magnet; and a servomechanismcapable of moving said stopper in parallel to said shaft according to arotating speed of said motor.
 4. An electric motor according to any oneof claim 1 to claim 3, wherein a lead angle of current supply by acontroller for controlling said controller is corrected according to apositional shift of a composite magnetic pole of said first field magnetand said second field magnet.
 5. An electric motor according to any oneof claim 1 to claim 3, wherein said first field magnet is fixed to ashaft, said second field magnet is separated from said shaft, said shaftand said second field magnet have screw functions to be connected toeach other by forming a bolt screw portion in said shaft and a nutportion inside said second field magnet, a displacement in an axialdirection of said second field magnet is detected, and a lead angle ofcurrent supply by a controller for controlling said inverter iscorrected corresponding to a positional shift angle of a compositemagnetic pole of said first field magnet and said second field magnet.6. An electric motor according to any one of claim 1 to claim 3, whereinsaid first field magnet is fixed to a shaft, said second field magnet isseparated from said shaft, and a plurality of supporting mechanismscapable of guiding rotational motion and reciprocal motion and thecomposite motion of said second field magnet is arranged between saidsecond field magnet and said shaft.
 7. A rotary electric machineaccording to any one of claim 1 to claim 3, wherein said first fieldmagnet is fixed to a shaft, said second field magnet is separated fromsaid shaft, and a sleeve is inserted between the inside of said secondfiled magnet and said shaft to fix said second field magnet to saidsleeve.
 8. A rotary electric machine according to claim 8, wherein saidsleeve is made of a non-magnetic material having an electric resistivityhigher than that of iron.
 9. An electric motor according to any one ofclaim 1 to claim 3, wherein said first field magnet is fixed to a shaft,said second field magnet is separated from said shaft, a plurality ofsprings is arranged before and after said second field magnet to guidethe rotational motion and the reciprocal motion and the composite motionof said second field magnet.
 10. An electric motor according to any oneof claim 1 to claim 3, wherein said first field magnet is fixed to ashaft, said second field magnet is separated from said shaft, adepressing portion is formed on a side surface of said first fieldmagnet where said first field magnet and said second field magnet are incontact with each other, a projecting portion also serving as a functionof said sleeve is formed in said second field magnet.
 11. An electricmotor according to any one of claim 1 to claim 3, wherein said firstfield magnet is fixed to a shaft, said second field magnet is separatedfrom said shaft, and a stopper is arranged at a position apart from aside surface of said second field magnet, said stopper having asupporting mechanism for guiding rotational motion and reciprocal motionand the composite motion to said second field magnet and said shaft. 12.An electric motor according to any one of claim 1 to claim 3, whereinsaid first field magnet is fixed to a shaft, said second field magnet isseparated from said shaft, an air gap between said rotor having saidsecond field magnet and said stator is larger than an air gap betweenthe rotor having said first field magnet and said stator.
 13. Anelectric motor according to any one of claim 1 to claim 3, wherein saidfirst and said second field magnets are opposite to the magnetic polesof said stator, and said first and said second field magnets arerelatively movable in the axial direction.
 14. A washing machineaccording to any one of claim 1 to claim 3, wherein said electric motoris operated by making positions of the magnetic pole centers of saidfirst field magnet and said second field magnet in phase during lowspeed operation, and by making the positions of the magnetic polecenters of said first field magnet and said second field magnet out ofphase during high speed and low load operation.
 15. A washing machineaccording to any one of claim 1 to claim 3, wherein said electric motoris operated by making positions of the magnetic pole centers of saidfirst field magnet and said second field magnet in phase during saidwashing or rinsing operation, and by making the positions of themagnetic pole centers of said first field magnet and said second fieldmagnet out of phase during spin-drying operation.